1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to new and improved elevator systems having supervisory control for controlling a plurality of elevator cars.
2. Description of the Prior Art
The main or lobby floor of a building is usually given special service by elevator systems, such as by attempting to maintain at least one car at the floor, which is called the next car. When there are no cars at the main floor, various arrangements are used in the prior art to return a car to the floor. For example, a dummy call for the main floor may be given to one or more of the cars, or the lowest down traveling car in the building may be caused to bypass hall calls and express to the main floor. The quota of cars which the system attempts to maintain at the main floor may change according to the time of day, such as by clock control, or automatically as the nature of the traffic demand changes.
Floors other than the main floor may be singled out for special attention, such as a convention floor, a restaurant floor, and the like. For example, at a certain time of the day, such as controlled by a clock, cars may be called to the special floor by dummy calls, in anticipation of heavy traffic.
Elevator systems of the prior art which use electromechanical relays in the car and supervisory control require additional wiring and control at the floors for which special service is to be provided, in order to provide the desired special functions, such as quota, next, dispatching, parking and spotting functions. Since this additional wiring and control is costly, it is usually provided for only one or two floors, even though other floors at various times of the day could benefit by having one or more of the special functions.
Copending application Ser. No. 467,700 filed May 7, 1974, entitled "Elevator System", which is assigned to the same assignee as the present application, discloses a new and improved elevator system in which wiring and controls are the same for all floors. A programmable system processor controls the strategy of answering requests for elevator service by the elevator cars. The lobby floor is identified in the instructions in the memory of the system processor, and thus the lobby or main floor instructions may be associated with any floor of the building by simply changing the instruction which identifies the lobby floor. This may be changed manually, such as by a switch, or automatically, such as by a clock or in response to actual traffic conditions. The "flexible" lobby of this copending application provides excellent service for any floor of the building which may experience an unusually heavy demand for traffic, but is primarily applicable to system processors which have a fairly large memory capacity, such as a minicomputer with at least 4K of core.
Copending application Ser. Nos. 503,146; 503,201; and 503,212, filed Sept. 4, 1974, now abandoned and incorporated into continuation-in-part applicatons 574,622, 574,829, and 574,664, respectively, which are assigned to the same assignee as the present application, disclose new and improved elevator systems in which the strategy utilized by the supervisory control is suitable for a microprocessor, such as Intel's MCS-4, and MCS-8, Rockwell's PPS, Signetic's PIP, National's GPC/P and AMI's 7300. These applications will be hereinafter referred to as the earlier filed copending applications. The microprocessor offers an attractive cost package as well as flexibility due to LSI circuitry and programmability. However, while the microprocessor offers programming flexibility at a modest cost, it imposes certain restrictions due to its relatively limited speed and memory capacity. It would be desirable to provide a new and improved universal operating strategy for giving special service to at least two selectable floors suitable for the operating speed and memory capacity of a microprocessor, which has the advantage of the hereinbefore mentioned copending application Ser. No. 467,700 of not requiring special wiring or hardware at any of the floors of the building.